Recently, as a solution for environmental problems, clean energy which can be obtained by wind power generation, solar power generation, or the like and can be used for household uses (for detached houses, etc.) or for industrial uses (for transport equipment, construction equipment, etc.) is attracting attention. However, the clean energy has a disadvantage in that output variation becomes large depending on the situation. For example, energy by the solar power generation can be obtained in the daytime where the sun is shining, while it cannot be obtained at night where the sun is down.
To stabilize the output of the clean energy, technology that temporarily stores the clean energy in a battery is used. For example, solar energy thus stored in the battery becomes available at night where the sun is down. In general, a lead battery has been used as a battery for storing the clean energy; however, the lead battery has a disadvantage in that it is generally large in size and low in energy density.
Thus, recently, a lithium ion secondary battery capable of operating at normal temperature and having a high energy density is attracting attention. In addition to the high energy density, the lithium ion secondary battery has a low impedance and is thus excellent in responsiveness.
As an example of an internal structure of such a lithium ion secondary battery, there is known a structure in which an electrode laminate obtained by laminating a plurality of sheet-like positive electrodes and a plurality of sheet-like negative electrodes through separators and electrolyte are housed in a laminate film exterior material having a rectangular shape in a plan view (refer to, e.g., Patent Document 1).